question about dockingpane

 

this is my codes:

MainFrm.h
CXTPDockingPaneManager m_paneManager;
CXTPDockingPane*    pPane1;//pane1   
CDlg1               Dlg1;
 
CXTPDockingPane*       pPane2; 
CDlg2             Dlg2; //pane2

MainFrm.cpp
create Funtion
pPane1= m_paneManager.CreatePane(IDR_PANE1,CRect(0, 0,240, 150), xtpPaneDockRight);
if(!pPane1)
{
 TRACE0("failed to create!\n");
 return -1;
}

pPane2= m_paneManager.CreatePane(IDR_PANE2,CRect(0, 0,240, 150), xtpPaneDockRight);
if(!pPane2)
{
 TRACE0("failed to create!\n");
 return -1;
}

m_paneManager.AttachPane(pPane1, pPane2);

LRESULT CMainFrame::OnDockingPaneNotify(WPARAM wParam, LPARAM lParam)
{
    if (wParam == XTP_DPN_SHOWWINDOW)
    {
        CXTPDockingPane* pPane = (CXTPDockingPane*)lParam;
       
        if (!pPane->IsValid())
        {
            switch (pPane->GetID())
            {
   case IDR_PANE1:
   {
    if (!::IsWindow(Dlg1.m_hWnd))
    {
     Dlg1.Create(IDD_DLG1, this);
    }
    pPane->Attach(&Dlg1);
    break;
   }
   case IDR_PANE2:
   {
    if (!::IsWindow(Dlg2.m_hWnd))
    {
     Dlg2.Create(IDD_DLG2, this);
    }
    pPane->Attach(&Dlg2);
    break;
   }
   }
        }
        return TRUE;
    }
    return FALSE;
}